Detection lamp equipped with light-emitting diode

ABSTRACT

The present application reveals a lamp and a method for detecting leaks in air-conditioning and refrigeration systems. The lamp uses one or more light-emitting diodes (LEDs) as a light source to detect fluorescent dyes that have been added to the air-conditioning or refrigeration system.

This application is a con of Ser. No. 09/722,908 Nov. 27, 2000 U.S. Pat.No. 6,710,363 and is a con of Ser. No. 10/758,208 Jan. 14, 2004 U.S.Pat. No. 6,855,944

FIELD OF THE INVENTION

The present application is for a lamp for detecting leaks in commercialand industrial air-conditioning and refrigeration systems and otherliquid recirculating systems such as those employing engine oil,transmission fluid and hydraulic fluid. The lamp uses a light-emittingdiode (LED) as a light source to detect fluorescent dyes that have beenadded to the air-conditioning or refrigeration system.

DESCRIPTION OF THE RELATED ART

Leak detection, materials detection and qualitative non-destructivetesting are well suited to techniques employing fluorescence detection.These techniques rely upon the unique physical property of variousmaterials to fluoresce when excited by certain wavelengths of visible orultraviolet (UV) light.

It is a well-known phenomenon that electromagnetic energy within thenear ultraviolet spectrum of approximately 315 to 400 nanometerwavelengths produces fluorescence in certain materials, e.g.,fluorescent dyes. These fluorescent materials absorb radiated energy atthe near UV wavelengths and re-radiate or emit it at a longer wavelengthin the visible spectrum. Thus, when fluorescent material absorbselectromagnetic energy in a specific excitation frequency band in aspecific wavelength range, the material can emit electromagnetic energyin a characteristic fluorescent emission frequency band within thevisible light spectrum. This phenomenon has enabled inspection anddetection techniques in which fluorescent dyes, inks or pigments areilluminated by lamps selectively filtered to emit only ultraviolet(invisible to the human eye) and then re-radiate with a highluminescence in the visible spectrum. Some newer fluorescent dyesrespond well to higher wavelengths of light in the visible violet andblue range in addition to the invisible UV range.

For example, the slow leakage of refrigerant from an air conditioningsystem is difficult to locate by any other means. The reason for thedifficulty is because the refrigerant escapes as an invisible gas atsuch a low rate and rapid diffusion that the concentration ofrefrigerant in air near the leak site is difficult to differentiate fromthat surrounding any other location along the system circulation lines.However, by adding into the circulating system a small amount offluorescent dye that is soluble in the refrigerant, the dye is carriedout of the system with the refrigerant and glows brightly at the leaksite when the area is swept with a UV lamp.

A similar procedure can be used to locate leaks of other fluids, such aslubricants, oils, fuels, heat transfer fluids or hydraulic fluids. OtherUV inspection techniques use fluorescent dyes or paint to detectfissures or stress cracks in structural members.

Conventional inspection lamps employ high intensity light sources(incandescent bulbs) operating at high temperatures to generate asufficient photon flux for detection applications and utilize filters toabsorb the undesirable wavelengths. These bulbs give off light owing totheir temperature (incandescence). The power of the lamps is very highin wattage and therefore the lamp produces heat. A black light filtercan be used but the filter is very restrictive and allows only UVwavelengths to be transmitted while all of the remaining wavelengths areabsorbed. These filters typically have a transmission efficiency of50–70% for the UV wavelengths (320–380 nm). To compensate for thelimited transmission efficiency, the power of the lamps is very high inwattage and therefore heat producing. These lamps are usually 20–150watts. Consequently, the life expectancy of the bulb is limited.

The fluorescent dyes used in this system typically have maximumexcitation in the range of 320–380 nm. Some newer dyes respond well tohigher wavelengths of light in the visible violet and blue range inaddition to the invisible UV range (340–440 nm). With these dyes,improved photographic-type blue filters are used with smaller, lowwattage lamps. These blue filters work well in lamps of 50 watts orless. At 50 watts, the lamps do not produce as much heat and althoughthe blue filter allows some visible light to be transmitted, the dyesare still acceptably excited. In most cases, the lamps using these bluefilters are also sold with special glasses (blue blocker glasses) thatblock the visible blue spectrum light transmitted through the bluefilters. These glasses assist the operator in finding the leaks andseeing the dye reaction to UV, blue and violet light. In addition, theseblue filters are much more prone to temperature damage and cracking thanthe black light filters. However, the transmission efficiency is greaterby about 10% as compared to that for the black light filters. Also, theblue filters and the blue blocker glasses make the dye more visible tothe technician.

Newer improved filters have been developed by applying a dielectriccoating, that does not effect the visible and lower spectrum of lighttransmission, to a piece of glass. Such filters are referred to asdielectric or dichroic filters. These terms are interchangeable.Dielectric refers to the process used, and dichroic is the type ofcoating applied, also known as thin-film coating. For example, dichroicfilters with a dielectric coating have been developed in theentertainment industry and have high levels of transmission. Thedichroic filter with a dielectric coating allows UV, blue and IRwavelengths to be transmitted while most visible wavelengths areblocked. Thus, this type of filter does not absorb the IR heat and has atransmission efficiency of over 90% for the desired wavelengths. Theseadvantages allow users to reduce the size and wattage of the detectionlamps.

Luminescence, on the other hand, is the result of electronic excitationof a material. The light-emitting diode (LED) is a p-n junction in whichan applied voltage yields a flow of current, and the recombination ofthe carriers injected across the junction results in the emission oflight. The process involved here is in effect electroluminescence. Theratio of the number of emitted photons to the number of electronscrossing the p-n junction is the quantum efficiency. LED emission isgenerally in the visible part of the spectrum with wavelengths from 400nm to 700 nm or in the near infrared with wavelengths between 700 and2000 nm.

Red, yellow and green light-emitting diodes are known. More than 20billion LEDs are produced each year. Visible LEDs are used as numericdisplays or indicator lamps and are sufficiently bright that a row ofred LEDs are used in an automobile spoiler to replace the conventionalrear-window brake light. Infrared LEDs are employed in optoisolators, intelevision remote controls, and as sources in optical communicationsystems. The applied voltage is near 2.0 volts. The current depends onthe application and ranges from a few milliamperes to several hundredmilliamperes. Thus, LEDs function with low power drain, at reducedtemperatures and have an extremely long life expectancy, e.g., five toten years or more, as compared to incandescent bulbs.

The present application reveals a lamp for detecting fluorescent dyes inan air-conditioning or refrigeration system. The lamp uses alight-emitting diode as a light source rather than conventionalUV-emitting light sources. Consequently, the lamp operates with lowpower drain, at reduced temperatures and has an extremely long lifeexpectancy as compared to conventional detection lamps equipped withincandescent bulbs.

SUMMARY OF THE INVENTION

The present application discloses a lamp and a method for detectingfluorescent dyes that have been added to an air conditioning orrefrigeration system, where the fluorescent dyes reemit light at awavelength greater than the wavelength of light emitted from the lamp.The lamp comprises a lamp housing, at least one light-emitting diodewithin the lamp housing and means for providing power to the lamp, wherethe light emitted from the lamp is restricted to a predetermined rangeeffective to enhance the reemission of light from the fluorescent dyes.

In preferred embodiments of the lamp, the diode is a blue light-emittingdiode or a UV light-emitting diode and the blue light-emitting diode isan indium gallium nitride semiconductor. In other preferred embodiments,the blue light-emitting diode is a laser diode and the laser diode is agallium nitride based laser diode.

In yet other preferred embodiments, the lamp further comprises aprotector ring connected to the lamp housing and a lens positionedwithin the protector ring. The lens can be a filter selected from thegroup consisting of black, red, amber, yellow, green, blue, indigo,violet, UV light and full spectrum filters. In other preferredembodiments, the lens is a dichroic filter and the lamp furthercomprises a blocker glass.

In more preferred embodiments, the lamp further comprises a plurality oflight-emitting diodes and each of the light-emitting diodes emits thesame color light.

The present application also discloses a method for detecting leaks inan air-conditioning or refrigeration system. The method comprises thesteps of inserting a fluorescent dye into an air-conditioning orrefrigeration system, running or operating the air-conditioning orrefrigeration system and inspecting the air-conditioning orrefrigeration system with a lamp comprised of housing, at least onelight-emitting diode within the lamp housing and means for providingpower to the lamp.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of a light-emitting diode.

FIG. 2 shows an embodiment of the detection lamp of the presentinvention equipped with a single LED light source.

FIG. 3 shows an embodiment of the detection lamp of the presentinvention equipped with a single LED light source and a lens.

FIG. 4 shows an embodiment of the detection lamp of the presentinvention equipped with multiple LED light sources.

FIG. 5 shows an embodiment of the detection lamp of the presentinvention equipped with multiple LED light sources and a lens.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is for a lamp and a method for detecting leaks inan air-conditioning or refrigeration system. The lamp uses alight-emitting diode (LED) as a light source for detecting a fluorescentdye that has been added to the air-conditioning or refrigeration system.

FIG. 1 shows a light-emitting diode. Power is applied to one side of theLED semiconductor through a positive power lead or anode 1 and a whisker4. The other side of the semiconductor is attached to the top of ananvil 7 that is the negative power lead or cathode 2. It is the chemicalmakeup of the LED semiconductor 6 that determines the color of the lightthe LED produces.

Semiconductors can be made of, for example, gallium arsenide, GaAs;gallium arsenide phosphide, GaAs_(1-x)P_(x); aluminum gallium arsenide,Al_(x)Ga_(1-x)As; aluminum gallium indium phosphide,(Al_(x)Ga_(1-x))_(y)In_(1-y)P; gallium indium arsenide phosphide,Ga_(x)In_(1-x)As_(y)P_(1-y), etc. LEDs can be used to produce infrared,red, amber, yellow, green, blue, indigo, violet, ultraviolet or evenwhite light. White light is a combination of red, green and blue light.Presently, it is possible to produce white light with a single LED usinga phosphor layer (yttrium aluminum garnet) on the surface of a blue(gallium nitride) chip. The blue light-emitting diode is preferred anduses an indium gallium nitride (InGaN) semiconductor 6.

A high impact plastic or epoxy resin enclosure 3 surrounds thesemiconductor 6 and has two main functions. It is designed to allow themost light to escape from the semiconductor and it protects the LEDsemiconductor from the surrounding environment. A lens 5 focuses thelight (view angle) escaping from the semiconductor. The entire unit istotally embedded in epoxy. This makes the LED virtually indestructible.There are no loose or moving parts within the solid epoxy enclosure.Therefore, the light-emitting diode is essentially a p-n junctionsemiconductor diode that emits light when current is applied. Bydefinition, it is a solid-state device that controls current withoutheated filaments and is thus very reliable.

The light-emitting diodes of the present invention include laser diodes.These laser diodes produce a narrower spectrum of light thanconventional LEDs. For example, Toshiba (Japan) has developed a galliumnitride (GaN) based blue diode that emits light at a wavelength of 417nm. This laser diode is comprised of ultra-thin layers of indium galliumnitride (InGaN). Nichia Chemical Industrial Co, Ltd. (Japan) hasdeveloped a laser diode that emits light in the violet spectrum. Thislaser diode uses a sapphire substrate. First, a 100 micron-thick galliumnitride (GaN) layer is formed on the sapphire substrate and then thesapphire substrate is removed by polishing to leave an 80 micron-thickGaN substrate.

FIG. 2 shows an embodiment of the detection lamp of the presentinvention equipped with a single LED. The detection lamp is comprised ofa lamp housing 10, a protector ring or cap 20, a single light-emittingdiode 30 within the lamp housing and a cable 40 for connection to apower source. Obviously, the housing can have any shape provided thatthe light from the LED is emitted from the housing.

The detection lamp can function without the use of filters, therebylowering the manufacturing cost. Since the size of the LED isconsiderably smaller than that of conventional incandescent bulbs, thedetection lamp can be miniaturized, thereby facilitating maneuveringinside an engine compartment and around an air-conditioning system of anautomobile. The inspection lamp equipped with an LED is extremelydurable, drop resistant and impact resistant, in part, because of theconstruction of the LED, as described above. Also, the inspection lampcan be made waterproof which is a great advantage in an automotiveservice environment exposed to numerous liquids and solvents.

Furthermore, the inspection lamp uses a very low current. For example,it can be operated with 2–5 volts. The lamp can be powered by AC, DC oreven solar power. Also, there is a constant output of light regardlessof voltage. There is very little heat produced and this is extremelyadvantageous for a mechanic working around the exposed enginecompartment of an automobile.

FIG. 3 shows an embodiment of the detection lamp of the presentinvention equipped with a single LED and a lens. The detection lamp iscomprised of a lamp housing 10, a protector ring or cap 20, which alsofunctions as a lens holder, a lens or filter 50, a single light-emittingdiode 30 within the lamp housing and a cable 40 for connection to apower source.

The lens functions to block out undesirable wavelengths emitted from theLED and to transmit only the desired wavelengths. For example, a blueLED emitting at 430–470 nm can be equipped with a filter blocking orreflecting wavelengths between 450–500 nm. Therefore, only wavelengthsbetween 430–450 nm will be transmitted from the lens. The lens may beselected from black light, blue light or any desired wavelength blockeror transmitter, even a full spectrum filter. Thus, dichroic filters maybe used in the present invention. Furthermore, a blocker glass can beused in conjunction with the lens, e.g., a blue blocker glass can beused with a blue filter or lens. The choice of the filter will depend onthe color emitted by the LED and the wavelength desired to betransmitted from the lamp.

The inspection lamp can be equipped with more than one LED, for example,2, 5, 10, 25 or more, to increase the light output of the lamp.Typically, the life expectancy of the blue LED exceeds 100,000 hours.

FIG. 4 shows an embodiment of the detection lamp of the presentinvention equipped with multiple LEDs. The detection lamp is comprisedof a lamp housing 10, a protector ring or cap 20, multiplelight-emitting diodes 30 within the lamp housing and a cable 40 forconnection to a power source.

In a preferred embodiment, each of the multiple light-emitting diodesemits the same color light. However, different color-emitting LEDs maybe used in the same lamp. Thus, a red LED, a green LED and a blue LEDcan be used to generate white light in the lamp.

FIG. 5 shows an embodiment of the detection lamp of the presentinvention equipped with multiple LEDs and a lens. The detection lamp iscomprised of a lamp housing 10, a protector ring or cap 20, which alsofunctions as a lens holder, a lens or filter 50, multiple light-emittingdiodes 30 within the lamp housing and a cable 40 for connection to apower source.

The following non-limiting examples are included to demonstratepreferred embodiments of the invention. It should be appreciated bythose skilled in the art that the techniques disclosed in the exampleswhich follow represent techniques discovered by the inventor to functionwell in the practice of the invention, and thus can be considered toconstitute preferred modes for its practice. However, those of skill inthe art should, in light of the present disclosure, appreciate that manychanges can be made in the specific embodiments which are disclosed andstill obtain a like or similar result without departing from theconcept, spirit and scope of the invention. More specifically, it willbe apparent that certain components may be substituted for thecomponents described herein while the same or similar results would beachieved. All such similar substitutes and modifications apparent tothose skilled in the art are deemed to be within the spirit, scope andconcept of the invention as defined by the appended claims.

EXAMPLES Example 1

7.5 ml of fluorescent dye (part no. 399006, UView Ultraviolet Systems,Inc., Mississauga, Ontario, Canada) were inserted into an automotiveair-conditioning system of a 1999 Mercedes ML430. The dye fluoresces inthe excitation range of 450–550 nm. The air-conditioning system wasturned on and allowed to run for one minute. The air-conditioning systemwas inspected for leaks using an ultraviolet lamp equipped with a bluelight-emitting diode. The lamp is shown in FIG. 2. The blue LED waspurchased from Hosfelt Electronics (part no. 25-368, Steubenville, Ohio)and emitted blue light in the range of 450–600 nm. Within one minute ofinspection, a leak was detected directly below the compressor andappropriate repairs made.

Example 2

7.5 ml of the same fluorescent dye used in Example 1 were inserted intoan automotive air-conditioning system of a 2001 Chrysler PT Cruiser. Theair-conditioning system was turned on and allowed to run for twominutes. The air-conditioning system was inspected for leaks using anultraviolet lamp equipped with five blue light-emitting diodes. The lampis shown in FIG. 4. The blue LEDs were purchased from HosfeltElectronics (part no. 25-368, Steubenville, Ohio) and emitted blue lightin the range of 450–600 nm. Within one minute of inspection, a leak wasdetected in a connection to the condenser and appropriate repairs made.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not limited to thedisclosed embodiments, but on the contrary is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

Thus, it is to be understood that variations in the present inventioncan be made without departing from the novel aspects of this inventionas defined in the claims. All patents and articles cited herein arehereby incorporated by reference in their entirety and relied upon.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

1. A lamp for detecting fluorescent dyes that have been added to an airconditioning or refrigeration system, wherein the fluorescent dyesreemit light at a wavelength greater than the wavelength of lightemitted from the lamp, the lamp comprising: a lamp housing; at least onelight-emitting diode within the lamp housing, the diode emitting lighthaving a wavelength band effective to enhance the reemission of lightfrom a fluorescent dye, and wherein said miniaturized lamp is sized tofacilitate maneuvering inside an engine compartment and around anair-conditioning system or refrigeration system.
 2. The lamp of claim 1,wherein the diode is a blue light-emitting diode.
 3. The lamp of claim1, wherein the diode is a UV light-emitting diode.
 4. The lamp of claim2, wherein the blue light-emitting diode is an indium gallium nitridesemiconductor.
 5. The lamp of claim 2, wherein the blue light-emittingdiode is a laser diode.
 6. The lamp of claim 5, wherein the laser diodeis a gallium nitride based laser diode.
 7. The lamp of claim 1, furthercomprising a protector ring connected to the lamp housing.
 8. The lampof claim 7, further comprising a lens positioned within the protectorring.
 9. The lamp of claim 8, wherein the lens is a filter selected fromthe group consisting of black, red, amber, yellow, green, blue, indigo,violet, UV light and full spectrum filters.
 10. The lamp of claim 9,further comprising a blocker glass.
 11. The lamp of claim 9, wherein thelens is a dichroic filter.
 12. The lamp of claim 1, further comprising aplurality of light-emitting diodes.
 13. The lamp of claim 12, whereineach of the light-emitting diodes emits the same color light.
 14. A lampfor detecting fluorescent dyes that have been added to an airconditioning or refrigeration system, wherein the fluorescent dyesreemit light at a wavelength greater than the wavelength of lightemitted from the lamp, the lamp comprising: a lamp housing comprising apower source; at least one light-emitting diode within the lamp housing,the diode emitting light having a wavelength band effective to enhancethe reemission of light from a fluorescent dye, and wherein saidminiaturized lamp is sized to facilitate maneuvering inside an enginecompartment and around an air-conditioning system or refrigerationsystem.
 15. The lamp of claim 14, wherein the power source is a directcurrent power source.
 16. The lamp of claim 14, wherein the power sourceis a solar power source.